1. Field of the Invention
This invention relates to a box fan of the type which has open front and rear grills with an air divider ring in the front grill to improve the efficiency of the fan.
2. Description of the Prior Art
Improving the air flow output of box fans without increasing the size or number of fan blades, or the horsepower of the driving motor is a goal of many fan designers.
It has been observed by smoke tests that fan grills with open corners tend to draw air into the front grill at the corners which air is then exhausted through the central area of the fan grill.
Various grill designs have been proposed to improve performance of the open grill fans with, for example, closed corners which reduces the grill area for air output, but this approach has not been found to increase the efficiency of the fans.
Inclusion of the air divider ring of the invention into the front grill increases both the fan efficiency, and the structural integrity of the front grill.